Non-vitreous inorganic articles are becoming increasingly important in commerce as high performance materials. For example, non-vitreous ceramic fibers are finding utility not only as high temperature insulating materials, but also as reinforcing materials in composite structures, for example, in metals, glasses and ceramics. The reinforcement application requires fibers to have a high tensile strength and a high modulus of elasticity.
It is known that an oxide ceramic must be fully dense and have a polycrystalline structure if it is to achieve optimum tensile strength and modulus of elasticity (E). Whenever porosity is present, reduced or lower tensile strengths and modulus of elasticity can be expected. To reduce porosity in inorganic materials, the process of sintering is used which is normally accompanied by growth of the crystallites. Unfortunately, large crystallites or grains have the effect of reducing the tensile strength of polycrystalline fibers. Thus, the improvement in tensile strength attributed to the reduction in porosity by sintering is partially offset by the larger crystallites which have grown during sintering. Therefore, to produce inorganic fibers with a high tensile strength and a high modulus of elasticity (E), a dense ceramic (minimum porosity) with the smallest crystallites possible is preferred.
It is known to use organic precursors to produce a second SiC phase in oxide ceramics. U.S. Pat. No. 4,010,233 discloses inorganic fibers wherein a metal oxide phase contains a second dispersed phase. In all cases, the dispersed pahse is an in situ precipitation or chemical reaction product; for the examples utilizing SiC, it is obtained via chemical reaction of an organic precursor. The particle size is dependent upon the firing conditions used; for example, time, temperature and atmosphere. E values up to 269 GPa (39.times.10.sup.6 psi) are reported.
U.S. Pat. Nos. 4,298,558 and 4,314,956 disclose alkoxylated and phenoxylated methyl polysilane which are useful for the preparation of fine grained silicon carbide-containing ceramics. Pyrolysis and reaction of the ceramic precursor polymers provide the silicon carbide-containing ceramics.